Patients with Crigler-Najjar Type I syndrome have lifelong jaundice and are treated with phototherapy identical to that used to treat neonatal jaundice. A previous study on this patient found that the most rapidly- formed bilirubin photoproduct is rapidly excreted; however, this isomer reforms native bilirubin in the intestinal lumen which can be reabsorbed. The purpose of this study was to determine the effect of intraluminal binding agents on bilirubin elimination.